1. Field of the Invention
The invention concerns a process and a device for improving the visibility in vehicles, in particular at night, bad weather and fog. The process facilitates the recognition by the vehicle operator of images of traffic scenes recorded outside the visible spectrum.
2. Description of the Related Art
An opto-electronic system for vehicles is disclosed in DE 40 07 646, which includes two infrared headlights in addition to the normal headlights, which infrared headlights use near-infrared emitting laser diodes as light sources. A CCD-camera for taking a video image of the actual traffic scene is mounted in the roof area of the vehicle. The video image is displayed to the vehicle operator on a LCD-display or is projected onto the windshield. The reproduced image contains supplemental information, which the vehicle operator could not see with his own eyes or could only see with great effort, in particular in darkness, bad weather and fog.
The CCD-camera is normally sensitive exclusively or primarily in the infrared, and provides an image in which the objects appear based on their visibility in infrared, which depends—depending upon whether far or near infrared images are taken—more or less upon the temperature of the objects. In order for the operator to better distinguish objects from each other, one could assign different colors to different thermal intensities and display these on a color display, such as described for example in JP 08127286 A1. Such a “thermal image” corresponds essentially to an unchanged spectral distribution of the infrared image of scene shifted into the visible spectrum.
It is proposed in JP 06121325 A1 to employ a camera which is sensitive in multiple different spectral ranges, and to assign to each of these spectral ranges respectively one color, in which color the corresponding partial image is displayed on a color display.
With all known systems the vehicle operator sees the traffic scene however only in pseudo-intensities or, as the case may be, pseudo colors. Such a manner of representing an image is uncustomary and foreign to humans, particularly with images taken in the far infrared. Thus, even a vehicle operator familiar with the system has the burden of processing the information represented in pseudo-intensities or, as the case may be, pseudo-colors, in comparison to color images which are obtained in the visible spectral range.